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Solution

The proposal is to extend the concept of wildcard ACL (‘*’) to support wildcard-suffixed ACLs (‘name*’).
This means that it would be possible to create ACLs of type: User:clientA has READ access on topic orgA* from hostA,
i.e clientA has READ access to all topics that start with `orgA` from hostA.
The concept of wildcard-suffixed ACLs would be applicable only to resource names.

Storage model

Currently, ACLs are stored on ZK under path /kafka-acl/<resource-type>/<resource-name>.

For example:
ACLs for topic topicName would be stored under /kafka-acl/Topic/topicName.
ACLs for consumer group groupId would be stored under /kafka-acl/Group/groupId.

An example ACL definition looks like:

$ get /kafka-acl/Topic/topicName
{"version":1,"acls":[{"principal":"User:clientA","permissionType":"Allow","operation":"Read","host":"*"},{"principal":"User:clientA","permissionType":"Allow","operation":"Write","host":"*"},{"principal":"clientB","permissionType":"Allow","operation":"Write","host":"host1"}]}

Current supported resource names are either full resource names like topicName or a special wildcard '*'.

$ get /kafka-acl/Topic/*
{"version":1,"acls":[{"principal":"User:clientA","permissionType":"Allow","operation":"Read","host":"*"}]}
which means that clientA has read access to all topics from all hosts.

The challenge here is that some resources like consumer groups don't have any defined naming convention and can have '*' in their names.

We Now, we extend the same storage model to store ACLs under wildcard-suffixed resource names like orgName* in a different location 'kafka-wildcard-acl'. Changes will first be stored at 'kafka-wildcard-acl-change'.

$ get /kafka-wildcard-acl/Topic/teamA*
{"version":1,"acls":[{"principal":"User:clientA","permissionType":"Allow","operation":"Read","host":"*"}]}

ACLs write path

The above storage model ensures that there are NO changes on the ACL write path.
Input resourceName would be treated the same way as earlier i.e. the appropriate ACLs would be rewritten at /kafka-acl/<resource-type>/<resource-name> locationWrite to a new location 'kafka-wildcard-acl'.

$ get /kafka-wildcard-acl/Topic/orgName*
{"version":1,"acls":[{"principal":"User:clientA","permissionType":"Allow","operation":"Read","host":"*"}]}

ACLs read path

On read path, we look for all matching ACLs when:

a) getMatchingAcls(resourceWithWildcardSuffix) is called.
b) authorize(…) is called.

Access would be allowed if there is at least one ALLOW matching acl and no DENY matching acl (current behavior is maintained). Note that the length of the prefix doesn't play any role here.

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